SLM and PTS peak-power reduction of OFDM signals without side information

Selected mapping (SLM) and partial transmit sequence (PTS) are well-known techniques for peak-power reduction in orthogonal frequency-division multiplexing (OFDM). We derive a simplified maximum likelihood (ML) decoder for SLM and PTS that operates without side information. This decoder exploits the fact that the modulation symbols belong to a given constellation and that the multiple signals generated by the PTS or SLM processes are widely different in a Hamming distance sense. Pairwise error probability (PEP) analysis suggests how SLM and PTS vectors should be chosen. The decoder performs well over additive white Gaussian noise (AWGN) channels, fading channels, and amplifier nonlinearities.     

Selected mapping without side information for PAPR reduction in OFDM

Selected mapping (SLM) is a technique used to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) systems. SLM requires the transmission of several side information bits for each data block, which results in some data rate loss. These bits must generally be channel-encoded because they are particularly critical to the error performance of the system. This increases the system complexity and transmission delay, and decreases the data rate even further. In this paper, we propose a novel SLM method for which no side information needs to be sent. By considering the example of several OFDM systems using either QPSK or 16- QAM modulation, we show that the proposed method performs very well both in terms of PAPR reduction and bit error rate at the receiver output provided that the number of subcarriers is large enough.     

Adaptive scalar quantization without side information

In this paper, we introduce a novel technique for adaptive scalar quantization. Adaptivity is useful in applications, including image compression, where the statistics of the source are either not known a priori or will change over time. Our algorithm uses previously quantized samples to estimate the distribution of the source, and does not require that side information be sent in order to adapt to changing source statistics. Our quantization scheme is thus backward adaptive. We propose that an adaptive quantizer can be separated into two building blocks, namely, model estimation and quantizer design. The model estimation produces an estimate of the changing source probability density function, which is then used to redesign the quantizer using standard techniques. We introduce nonparametric estimation techniques that only assume smoothness of the input distribution. We discuss the various sources of error in our estimation and argue that, for a wide class of sources with a smooth probability density function (pdf), we provide a good approximation to a "universal" quantizer, with the approximation becoming better as the rate increases. We study the performance of our scheme and show how the loss due to adaptivity is minimal in typical scenarios. In particular, we provide examples and show how our technique can achieve signal-to-noise ratios within 0.05 dB of the optimal Lloyd-Max quantizer for a memoryless source, while achieving over 1.5 dB gain over a fixed quantizer for a bimodal source.     

On decoding of block codes with peak-power reduction in OFDMsystems

This letter discusses the decoding of a block-coded scheme proposed for orthogonal frequency division multiplexing peak power reduction, employing the ordered statistic decoding algorithm. Performance is evaluated by computer simulations over an additive white Gaussian noise channel and compared with the union bound. It is shown that with respect to optimum decoding, significant computational reduction can be achieved without noticeable error performance degradation     

Asymptotic analysis of unslotted frequency-hop multiple-access without side information

In a packet radio network that employs frequency-hop transmission and error control coding, the use of side information permits identification and erasure of symbols that have been corrupted by multiple-access interference, and thus greatly enhances multiple-access capability. In one approach, side information is generated from an error detecting random code. We investigate the trade-off between the reliability of side information and the rate of the code, and derive the maximum allowable code rate to achieve a certain reliability of side information. An achievable region and the channel throughput are examined for an unslotted frequency-hop packet radio network that employs Reed-Solomon codes and side information generated within the radio by an error detecting code.     

Signal shaping for peak-power and dynamics reduction intransmission schemes employing precoding

Precoding, i.e., nonlinear pre-equalization, at the transmitter side has been proved to be a very efficient strategy for channel equalization in single-carrier digital transmission schemes. It enables the application of coded modulation in a seamless fashion. A drawback of precoding is that the signal at the input of the decision device exhibits a huge dynamic range. Based on dynamics shaping, a combined precoding/shaping technique introduced in the paper by Fischer et al. (1995), a new shaping strategy is developed in this paper. This technique enables a flexible tradeoff among: (1) reduction of the average transmit power; (2) avoidance of peaks in the transmit signal in order to facilitate line driver implementation; and (3) restriction of the maximum amplitude at the receiver side to a prescribed value. Over a wide range, all three demands can be met simultaneously. As the scheme is fully compatible with Tomlinson-Harashima (1971, 1972) precoding, it can replace the precoder even in existing and standardized schemes. Simulation results for a typical digital subscriber line scenario show the achievable gains     

An adaptive quantization algorithm without side information for depth map coding

This paper presents a novel block-adaptive quantization scheme for efficient bit allocation without side information in depth map coding. Since the type of distortion in a depth map causes different effects in terms of the visual artifacts in a synthesized view, the proposed method adaptively assigns the number of bits according to the characteristics of the corresponding texture block. I have studied the details of the depth map and its rendered view distortion, modeled these analytically, and then proposed a new rate and distortion model for depth map coding. Finally, I derived a simple closed-form solution based on my proposed rate and distortion model, which determines the block-adaptive quantization parameter without any side information. Experimental results show that the proposed scheme can achieve coding gains of more than 0.6% and 1.4% for quarter- and full-resolution depth maps, respectively, in a multi-view-plus-depth 3D system.     

Improved SLM algorithm for PAPR reduction in OFDM system

In order to reduce the peak to average power ratio (PAPR) of the conventional selective mapping (SLM) algorithm,decrease the transmission of side-band information,and improve the spectral efficiency in the orthogonal frequency division multiplexing (OFDM) system,the TL-SLM algorithm based on the conversion matrix and the chaotic sequence was proposed firstly.Although the TL-SLM algorithm could effectively decrease the transmission of side-band information,the reduction of PA P R was limited.To solve this problem,an improved TL-SLM algorithm based on the rotation vector was proposed,which was the TR-SLM algorithm.TR-SLM algorithm introduced the rotation vector to generate more time-domain alternative signals to further reducing the PA P R.The performance analysis shows that although the TL-SLM algorithm and the TR-SLM algorithm increase the complexity a little,the PA P R performance is effectively improved and the transmission of side-band information is greatly reduced.     

一种基于SLM的抑制PAPR的改进算法研究

正交频分复用(OFDM)作为一种特殊的多载波传输(MCM)方案,具有较高的频带利用率和良好的抗多径干扰能力。但较高的峰均功率比(PAPR)是限制其应用的一个主要缺点。选择性映射(SLM)算法是无失真降低OFDM系统PAPR的有效方法,但其复杂度较高。因此提出了一种基于SLM的抑制PAPR的改进算法。仿真结果表明,该方法即有效地降低了SLM实现的复杂度,又大幅降低了PAPR,提高了OFDM系统性能。     

SLM based PAPR reduction of OFDM signal using new phase sequence

One of the main issues of orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR) of the transmitted signal which adversely affects the complexity of power amplifiers. The selected mapping (SLM) technique is one of the promising PAPR reduction techniques for OFDM. In this reported work, rows of normalised Riemann matrices are selected as phase sequence vectors for the SLM technique. MATLAB simulations show PAPR reduction of around 2.3 dB using the proposed method compared with methods reported in the literature.     

Control information transmission without resource consumption for PAPR reduction of OFDM signal

A peak-to-average power ratio (PAPR) reduction method for orthogonal frequency division multiplexing (OFDM) signals is proposed that requires no additional resources to transmit side information. The approach used to reduce PAPR is based on selected mapping (SLM). SLM produces several candidates of OFDM symbols, the subcarrier phases of which are rotated, and the OFDM symbol that yields the minimum PAPR is selected and transmitted to the receiver. To cancel the rotation used to generate the original signal at the receiver, transmission of side information using a time slot is usually required. This decreases the efficiency with which data can be transmitted. The proposal is to modify SLM so as to implant the side information into the OFDM data symbol. This results in no efficiency loss. Additionally, the error rate in estimating the side information is extremely low when enough subcarriers are used to carry the side information. The performance of the method is confirmed by numerical simulation. The PAPR improvement equals that of the original SLM. The implanted side information was transmitted with high reliability.     

光OFDM系统中一种改进的SLM峰均比抑制方案

针对光正交频分复用(O-OFDM)系统中峰值平均功 率比(PAPR)较高的缺点,对PAPR抑制技术的选择性 映射法(SLM) 进行了深入研究。基于低复杂度SLM方案的深入研究,提出了一种改进的次PAP R选择的思 想与低复杂度SLM相结合的PAPR抑制方案。改 进的SLM方案能够成倍降低传统SLM方案的计算复杂 度。仿真分析表明,改进的SLM方案在载波数为256的O-OFDM系统中,计算复杂度能降低50%以上,并 且随着子载波数的增加,其复杂度降低程度更为高效;同时,该改进的SLM方案又能使其PAPR抑制性能优于传统的SLM方案,从而进一步提升了低复杂度SLM 方案的实用价值。     

Universal portfolios with side information

We present a sequential investment algorithm, the μ-weighted universal portfolio with side information, which achieves, to first order in the exponent, the same wealth as the best side-information dependent investment strategy (the best state-constant rebalanced portfolio) determined in hindsight from observed market and side-information outcomes. This is an individual sequence result which shows the difference between the exponential growth wealth of the best state-constant rebalanced portfolio and the universal portfolio with side information is uniformly less than (d/(2n))log (n+1)+(k/n)log 2 for every stock market and side-information sequence and for all time n. Here d=k(m-1) is the number of degrees of freedom in the state-constant rebalanced portfolio with k states of side information and m stocks. The proof of this result establishes a close connection between universal investment and universal data compression     

Adaptive action selection without explicit communication formultirobot box-pushing

The paper describes a novel action selection method for multiple mobile robots box-pushing in a dynamic environment. The robots are designed to need no explicit communication and be adaptive to dynamic environments by changing modules of behavior. The various control methods for a multirobot system have been studied both in centralized and decentralized approaches, however, they needed explicit communication such as a radio, though such communication is expensive and unstable. Furthermore, though it is a significant issue to develop adaptive action selection for a multirobot system to a dynamic environment, few studies have been done on it. Thus, we propose action selection without explicit communication for multirobot box-pushing which changes a suitable behavior set depending on a situation for adaptation to a dynamic environment. First, four situations are defined with two parameters: the existence of other robots and the task difficulty. Next, we propose an architecture of action selection which consists of a situation recognizer and sets of suitable behaviors to the situations and carefully design the suitable behaviors for each of the situations. Using the architecture, a mobile robot recognizes the current situation and activates the suitable behavior set to it. Then it acts with a behavior-based approach using the activated behaviors and can change the current situation when the environment changes. We fully implement our method on four real mobile robots and conduct various experiments in dynamic environments. As a result, we find out our approach is promising for designing adaptive multirobot box-pushing     

Low-complexity PAPR reduction technique for OFDM systems using modified widely linear SLM scheme

In this paper, a modified widely linear selective mapping (MWL-SLM) scheme is proposed to reduce the peak-to-average power ratio (PAPR) of the orthogonal frequency-division multiplexing (OFDM) systems. In the proposed MWL-SLM scheme, through partition one complex signals into two real signals and combining the linear properties of the Fourier Transform, at most 4M² candidate signals can be obtained but only require M inverse fast Fourier transform (IFFT) operations. As a result, the proposed SLM scheme has the ability to generate more candidates when compared with conventional SLM (C-SLM) and widely linear SLM (WL-SLM). Therefore, MWL-SLM outperforms C-SLM and WL-SLM for the same computational cost of IFFT operations. Alternatively, for a given number of candidates, MWL-SLM has slightly inferior PAPR reduction performance to C-SLM and WL-SLM but requires less IFFT operations to be implemented, thus resulting in a lower computational complexity. Simulation results demonstrate the effectiveness of the proposed scheme.     

Adaptive space-time transmission with side information

In this letter, a simple adaptive transmit diversity technique with side information is presented. The proposed scheme has a number of attractive characteristics. First, it is simple to implement. Second, it is efficient in terms of bandwidth requirements for side information feedback. Finally, it adapts to the quality of the side information to accordingly configure the space-time signal set to be transmitted so that additional gain in signal-to-noise ratio can be achieved at the receiver. In effect, it can be viewed as a flexible combination of suboptimal beamforming and space-time block coding.     

Watermarking as communications with side information

Several authors have drawn comparison between embedded signaling or watermarking and communications, especially spread-spectrum communications. We examine the similarities and differences between watermarking and traditional communications. This comparison suggests that watermarking most closely resembles communications with side information at the transmitter and or detector, a configuration originally described by Shannon (1958). This leads to several novel characteristics and insights regarding embedded signaling which are discussed in detail     

SLM‐based PAPR reduction method using partial data circulation and side information insertion in OFDM systems

In this paper, two selected mapping (SLM)‐based schemes are proposed to reduce the peak‐to‐average power ratio (PAPR) in the orthogonal frequency division multiplexing (OFDM) systems. One is SLM‐based partial data circulation (PDC) scheme. The other is SLM‐based PDC with hamming coded side information (SI) scheme. In the PDC scheme, the partial samples within the data sequence are scrambled by circularly shifting to obtain a set of candidate sequences and, then, each sequence is combined with the corresponding SI to form the candidate OFDM symbol. With the selection of the candidate OFDM symbols with the lowest PAPR, the PAPR of the transmitted signal could be greatly reduced. In the other scheme, hamming code is used to protect the SI to improve the system performance. Simulation results show that the proposed method could reduce PAPR and it has a better bandwidth efficiency and less modules of inverse fast Fourier transform than that with the SLM‐based dummy sequence insertion scheme. Copyright © 2008 John Wiley & Sons, Ltd.     

On causal source codes with side information

We study the effect of the introduction of side information into the causal source coding setting of Neuhoff and Gilbert. We find that the spirit of their result, namely, the sufficiency of time-sharing scalar quantizers (followed by appropriate lossless coding) for attaining optimum performance within the family of causal source codes, extends to many scenarios involving availability of side information (at both encoder and decoder, or only on one side). For example, in the case where side information is available at both encoder and decoder, we find that time-sharing side-information-dependent scalar quantizers (at most two for each side-information symbol) attains optimum performance. This remains true even when the reproduction sequence is allowed noncausal dependence on the side information and even for the case where the source and the side information, rather than consisting of independent and identically distributed (i.i.d.) pairs, form, respectively, the output of a memoryless channel and its stationary ergodic input.     

Channel simulation and coding with side information

Studies the minimum random bit rate required to simulate a random system (channel), where the simulator operates with a given external input. As measures of simulation accuracy the authors use both the variational distance and the d¯ distance between joint input-output distributions. They find the asymptotic number of random bits per input sample required for accurate simulation, as a function of the distribution of the input process. These results hold for arbitrary channels and input processes, including nonstationary and nonergodic processes and do not hinge on a specific simulation scheme. A by-product of the analysis is a general formula for the minimal achievable source coding rate with side information